(a) Field of the invention
The present invention relates to an obstetrical instrument for use to rupture the foetal membranes of a pregnant woman in order to release the amniotic fluid trapped by these memboranes and thus to induce labour prematurely, to facilitate delivery and/or to reduce the internal pressure within the uterus.
(b) Background of the invention
Numerous instruments are known and commonly used by the obstetricians to rupture the foetal membranes of a pregnant woman for anyone of the above mentioned reason. By way of example, reference can be made to the instruments disclosed in U.S. Pat. No. 3,410,269 issued on Nov. 12, 1968 to J. H. Hovick and in U.S. Pat. Nos. 3,533,411 and 3,624,747 issued on Oct. 13, 1970 and Nov. 30, 1971 respectively both in the name of C. A. MaKnight and A. L. GILBERT.
The obstetrical instruments disclosed in these U.S. patents are rather efficient in practice, in addition of being easily suppliable in quantity and disposable form at a relatively low cost and in sterile condition. These known instruments are designed to reduce as much as possible the possibility of injuring the unborn foetus or damaging the mother's internal tissue. It should indeed be understood that this kind of instrument is used almost entirely by "feel", since the obstetrician cannot see the membranes to be ruptured nor the part of the instrument in contact with the membranes.
The problem with these known instruments is that they always have a sharp end with the sharp tip to puncture or rupture the membranes, even if this sharp end is retractable into a vaginal shielding body as disclosed in U.S. Pat. No. 3,410,263, or is in recess with respect to a blunt and nearly flat end surface as disclosed in U.S. Pat. Nos. 3,624,747 and 3,533,411.